1. Field of the Inventions
The present inventions relate to a control system for watercraft propulsion units and particularly to a watercraft control system having three or more watercraft propulsion units disposed in parallel in a hull.
2. Description of the Related Art
Some watercraft can have three outboard motors mounted on a transom thereof, in a side-by-side arrangement. Conventionally, such watercraft incorporate three sets of shift and throttle levers, each of which corresponds to a respective outboard motor. However, it can be a burden for the operator to operate six shift and throttle levers in addition to operating a steering device.
Recently, an improved control device for a watercraft that can control the entire shift and throttle operations of three outboard motors with two levers disposed transversely next to each other has been suggested. For example, the i6000 series, shift/throttle lever for three outboard motors, available from the Teleflex Morse Co., Ltd. (USA) is such a device.
Using such a device, the operator can control operations of the outboard motor located on the right hand side (hereinafter called “starboard side outboard motor”) using the lever positioned on the starboard side, while the operator controls operations of the outboard motor located on the left hand side (hereinafter called “port side outboard motor”) using the lever positioned on the port side. The outboard motor centrally located between the starboard side outboard motor and the port side outboard motor is controlled in accordance with operational conditions of the starboard side outboard motor and the port side outboard motor. That is, if the starboard side outboard motor or the port side outboard motor is controlled to be in a forward mode and the other one of those motors is controlled to be in a reverse mode, the center outboard motor is controlled to be in a neutral mode. If both of the motors are controlled to be in the same mode, the center outboard motor is also controlled to be in the same mode and in the same throttle opening as those of the starboard side outboard motor or the port side outboard motor.
During operation, however, an operator may decide to turn either leftwardly or rightwardly while advancing (or reversing). In other situations, for example in tight spaces in a marina or when moving a watercraft alongside a wharf or dock, an operator may attempt to turn at slow speed, without moving forwardly or rearwardly, (“turning round on the spot”). In some cases, “turning round on the spot” is performed while a greater thrust is applied for the advancing or reversing, to cancel wind drift of the watercraft.
However, in such a case, since in the foregoing operating device, the central outboard motor is set in neutral or operates in the same way as either the left or the right outboard motor. Thus, the central outboard motor either interferes with the desired maneuver, or it is not used efficiently. For example, if either of the left and the right outboard motor is driven for advancing and the other for reversing to effect turning of the hull, the central outboard motor is set in neutral unconditionally, so that the central outboard motor cannot be used effectively in response to the conditions, for example, of turning round in advancing or reversing.
Also, if both of the left and right outboard motors have thrusts in the same direction but different in magnitude, since the central outboard motor is driven to be suited to one of the left and right outboard motors, an awkward feeling may be given or unnecessary thrust may be generated. In some cases, against the thrust on the side of the left unit (or the right unit) increased by the central outboard motor, the other outboard motor or the right unit (or the left unit) is required to generate a larger thrust, to counterbalance the turning moment which affects the moving direction of the watercraft